Dampers, known as particle vibration dampers are known from U.S. Pat. No. 6,547,049. These dampers comprise a hollow volume filled with particles up to around 95% volume fill. As explained in this patent, the particle vibration damper operates by particle interface contact friction whereby the frictional forces are dependent upon material type and contact forces, the contact forces being governed by the vibratory accelerations of the wall. Under specific vibrations a particle will attempt to migrate through the vibration damper device in a direction that is generally parallel to the polar axis and competes with the other particles for their migratory position. Three analogous phases of movement may be identified: solid, liquid and gas, with each phase being dependent on the volume fill of the chamber with the particles. The gas phase can only occur if the particles can behave like molecules in a gas, which, in most embodiments, is significantly below 95% fill. The fluid phase of motion is where the particles “fluidise” and the motion of the particles are similar to a viscous liquid; at least one free surface is required. The solid phase is where the particles migrate around the chamber without colliding or fluidising and requires almost a full volume fill. The most effective damping region is the boundary between the solid and fluid phase usually around a 90-98% fill. Vibratory energy is dissipated by the inter-particle frictional forces thus providing damping to vibrations.
Particle dampers of this type are usually separate containers attached to a surface of the component to be damped. Where the outside form of the component is important for perhaps aerodynamic, thermal or geographic reasons, such particle dampers may be difficult to use. Additionally, the method of attaching the damper limits the locations of the component on which the damper may be placed. Many components have an optimum damping location and if this location is inaccessible for placement of the damper, larger, heavier and less efficient dampers may be necessary at other, more accessible, locations of the component.
Solid freeform fabrication (SFF) techniques are methods, which allow the manufacture of solid objects by sequential delivery of energy and/or material to specified locations to produce that object. SFF is sometimes referred to as rapid prototyping, rapid manufacture, layered manufacturing and additive manufacture.
A number of techniques are known in the art including: three-dimensional printing using an inkjet-like printhead to deposit phase change material in layers, stereolithography which uses a laser to cure liquid photopolymers, fused deposition modelling which extrudes hot plastic through a nozzle, Direct Laser Deposition (DLD) where a laser is used to melt metal from a wire or powder and deposit it on the part directly, and Selective Laser Sintering (SLS) or powder bed processing which uses a laser or other heat source to fuse powdered nylon, elastomer or metal layered in a bed of the material.
In Direct Laser Deposition is a melt pool is formed in a substrate and a feedstock, typically a metal powder, is directed into the melt pool and allowed to solidify by traversing the heat source away from the deposition location. By repeated melting and deposition at the same location it is possible to create quite complex structures.
One technique for manufacturing complex three-dimensional shapes is described in U.S. Pat. No. 6,656,409. A laser is used as the heat source to simultaneously heat the deposition substrate and a powder feedstock. The laser beam is focused to provide a high irradiance area at or near the surface on which the deposition is to occur. At or near the deposition region the powder feedstock material intersects the laser beam and becomes molten to create a new layer of material on the substrate.